Single Stack Smudge Pot
Developed in Southern California in 1913 after a freeze wiped out an entire crop, a smudge pot is a device with a round base and a chimney protruding from the center at the top of the base. The purpose of a smudge pot is to prevent the accumulation of frost on a grove of fruit trees. Crude oil is placed in the round base of the pot and burned to produce smoke and heat to stave off potentially damaging frost. The smoke from the smudge pots work to create a blanket that will reduce heat loss around the fruit trees in the orchard.
Cambered-Neck Smudge Pots
Some smudge pots have a tall, cambered neck in the center with a pipe feed out of the chimney's side, which recirculates stack gas back into the burn chamber for better combustion. These cambered-neck smudge pots work with filler caps that have a three- or four-flue opening, which allows for better burn control. An oil-soaked wood chip is placed inside the neck to help light the fuel in the pots.
Smudge pots work when they are placed between the trees in a fruit orchard and ignited when temperatures reach 29 degrees Fahrenheit. On the cambered-neck pots, one flue is open at 29 degrees, and one more is opened for every degree below 29 degrees. These smudge pots offer maximum protection at 25 degrees Fahrenheit. If the temperature dips below 25 degrees, the smoke blanket created by the smudge pots may or may not help.
Smudge pots were widely used by citrus farmers for 70 years before the price of oil escalated during the 1970s. Environmental concerns also played a role in the decreasing prevalence of smudge-pot protection. Today, many citrus farmers use smokeless burners that are fueled by natural gas to heat the orchards in the event of frost.
In the early 1900s, smudge pots also worked as warning markers for road construction. Today, you can find decorative smudge-pot-style lanterns that burn lamp oil or citronella oil. These decorative smudge pots have a wick in the center where the stack or neck would be on a real smudge pot, and they work as a light source or as protection from mosquitoes.